Thermostat with manual reset

ABSTRACT

A structurally simple low cost manual reset thermostat is disclosed. The thermostat includes a one piece body and two terminal assemblies. The rivet of one terminal assembly connects the switch arm and a reset retainer. The switch arm retains a snap disc in its assembled position. Four guide projections with two on each side of the spring arm laterally locate the snap disc. A reset member is positioned by the guide projections and is arranged to engage the snap disc on opposite sides of the spring arm. Stops are provided to prevent overstressing of the disc by the reset member.

United States Patent 1151 3,660,793 Them et al. 1451 May 2, 1972 54]THERMOSTAT WITH MANUAL RESET 3,322,920 5/1967 Morris ..337/365 [72]Inventors: Edward G. Them; Walter C. Kowalski, FQREIGN PATENTS 0RAPPUCATIONS both of Mansfield, Ohio v 691,167 5/1953 Great Brltain..337/91 [73] Assignee: Therm-O-Disc, Incorporated, Mansfield,

Ohio Primary Examiner-Bemard A. Gilheany Assistant ExaminerDewitt M.Morgan [22] Flled' 1970 Attorney-McNenny, Farrington, Pearne & Gordon[21] Appl. No.: 24,605

[57] ABSTRACT [52] U.S. Cl ..337/348, 337/380 A r c urally simple lowcost manual reset thermostat is dis- I 51 1111.0 ..H0lj 37/54, 11011137/70, H01h 37/74 closed- The thermostat includes a one Piece y and two[58] Fie|d f Search; 337 9 3 3 354 3 7 3 2 minal assemblies. The rivetof one terminal assembly connects 337/380 the switch arm and a'resetretainer. The switch arm retains a snap disc in its assembled position.Four guide projections [56] References Cited with two on each side ofthe spring arm laterally locate the snap disc. A reset member ispositioned by the guide projec- UNITED STATES PATENTS tions and isarranged to engage the snap disc on opposite sides of the spring arm.Stops are provided to prevent overstressing 2,839 637 6/1958 Epsteln..337/9l ofthe disc by the reset'member 2,426,906 9/1947 Vaughan.......337/9l X A 3,428,932 2/1969 Menecke ..337/348 4 Claims, 6 DrawingFigures j- 47 Z 2. jg 33 4a 14 .42 43 v nr: :2:

v 28 A 5 Z /0 l 1 22 1' fi -:2 g 7 I 4/ -1 2/ THERMOSTAT WITH MANUALRESET BACKGROUND OF THE INVENTION This invention relates generally tobimetallic snap disc thermostats and more particularly to a novel andimproved manual reset thermostat of such type.

PRIOR ART The U.S. Letters Patent to Morris, No. 3,322,920, assigned tothe assignee of the present invention, discloses a simple, low costthermostat. In this thermostat the structure is arranged to require aminimum number of parts and to minimize the labor required for assembly.The thermostat provides a single body member, two terminal assemblies, aspring switch arm secured to one terminal assembly, and engagable withthe other, and a bimetallic snap disc for operating the switch arm. Thestructure is arranged'so that the disc is retained in position withinthe "body by the switch spring arm and so that only two rivets arerequired to, assemble all of the elements of the thermostats. Since arelatively small number of parts are required, and since assembly costsare low, the thermostat is low in cost even though it provides reliableand accurate operation.

SUMMARY OF THE INVENTION The present invention permits the manufactureof a thermostat of the type disclosed by Morris wherein the thermostatis a manual reset device. The manual reset feature is added to athermostat of the type illustrated by Morris without substantiallyincreasing the cost of theentire device.

The illustrated thermostat incorporating this invention includes asingle body member with two terminal assemblies riveted thereon. Aspring arm is secured at one end to one terminal assembly and provides afree arm portion engagable with the other terminal assembly. The disc isretained in the position within the body assembly by the spring arm. Thebody is formed with locating projections which laterally locate the discin its assembled position. The same projections laterally position areset member and limit the movement of the reset member to preventdamage to the disc. A single retaining element secured to one of theterminal assemblies retains'the reset member in position.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a plan view of a thermostatincorporating this invention;

FIG. 2 is a side elevation in longitudinal section taken generally along2-2 of FIG. 1 illustrating thestructural arrangement of the thermostatwhen the thermostat switch is I trating the body structure for retainingthe disc and the associated structure of the reset member.

DETAILED DESCRIPTION OF THE DRAWINGS The illustrated embodiment of thisinvention includes a molded body member preferably formed of a plasticmaterial such as a phenolic resin. The body is generally rectangular inshape and is provided with openings 11 at its ends for mounting thethermostat on the associated devices. A switch recess 12 is formed inthe central portion of the body 10 to receive the operating mechanism ofthe thermostat. A first terminal assembly 13 is mounted on the body 10and includes a rivet 14 and a terminal element 16. A second terminalassembly l7'is mounted on the body 10 at a location spaced from thefirst terminal assembly 13 and includes a rivet 18 and a terminalelement 19.

A cantilever spring contact arm 21 is mounted at one end by the rivet 18and is provided with a free arm portion which extends to a position overthe rivet 14. A contact 22 secured to the spring arm 21 is engagablewith the rivet 14 when the switch is closed and is moved to a positionspaced from the rivet 14 when the switch is open.

A bimetallic snap disc 23 is positioned between the spring arm 21 and acentral projection 24 formed on a web portion 26 integrally fonned onthe body 10. Lateral positioning of the disc is provided by foursubstantially symmetrically positioned guide projections 27, 28, 29, and30, integrally formed in the body 10. These guide projections arearranged with two spaced projections on each side of the spring arm 21.

The various elements are proportioned so that when the snap disc 23 isin one position of stability as illustrated in FIGS. 2 and 3, thecontact 22 engages the rivet I4 and the switch is closed. However, whenthe disc snaps through to its other position of stability as illustratedin FIGS. 4 and 5, the.

spring arm 21 is deflected upwardly, as illustrated in the drawings,causing openingof the switch. In the open position the spring arm 21engages diametrically opposite edges of the disc and the center portionof the disc rests against the central projection 24. Reference maybemade to the Morris patent, supra, for a more detailed description of thestructure and operation of the basic thermostat and the Morris patent ishereby incorporated by reference for such details.

Manual reset is provided by a structure including a reset member 32 anda retainer member 33. The shape of the reset member 32 is bestillustrated in FIG. 6. The reset member 32 is preferably molded from aplastic material and includes a cross portion 34 which extends betweentwo substantially parallel wall sections 36 and 37. Extending from thelower ends of the wall sections 36 and 37, respectively, are disc en?gaging projecting portions 38 and 39. The length of the portions 38 and39 is less than the spacing between the associated guide projections 27through 30 so that theseportions can extend down between the guideprojections and engage the edges of the disc 23 with one projection oneach side of the spring arm 21. I

The reset retainer 33 is preferably formed of flat metal stock shaped toprovide a mounting portion 41 secured under the head of .the rivet 18,two upstanding portions 42 and 43, and a central portion 44 whichextends substantially parallel to the spring arm. The central portion 44extends between the 'walls 36 and 37 and on the side of the crossportion 34 opposite the spring arm 21. A clearance opening 46 is formedin the central portion 44 substantially in alignment with the centerportion of the disc 23. A projection 47 on the reset member 32 extendsthrough the opening 46 to assist in locating the reset member.

The various elements are proportioned so that the projections 38 and 39are spaced from the disc 23 when the disc is in the position of FIGS. 2and 3 and the switch is closed. At this time the stop surfaces 48 engagethe tops of the adjacent projections 27 through 30 to limit the movementofthe reset member in a direction toward the disc. However when the discsnaps through to its opposite position of stability as illustrated inFIGS. 4 and 5, the lateral edges of the disc on opposite sides of thespring arm 21 engage the portions 38 and 39 and raise the reset memberto the illustrated position.

When reset is desired, the reset member 32 is pressed downward causingthe portions 38 and 39 to press down against the edges of the disc onopposite sides of the spring arm 21 and deflect the disc toward itsfirst position of stability. However, because of the engagement of thestop surfaces 48 with the top of the associated guide projections, themovement of the reset member is limited and overstressing of the disccannot occur. Therefore the disc calibration cannot be changed by theoperation of the reset. When trip-free operation is required, thevarious elements are proportioned so that the disc will hold the switchopen if it remains above a reset temperature even when the reset memberis fully depressed. With such an arrangement the disc will only snapback through its initial position and allow the switch to close if thedisc is below a reset temperature.

The end .of the portion 43 of the retainer engages the body at alocation spaced from the first terminal assembly 13 on the side oppositethe second terminal assembly 17 to provide support for the free end ofthe retainer. With this structure any downward force applied to thecentral portion 44 of the retainer is supported at both ends thereof.Upward forces of the free end of the retainer 33 normally are notencountered so it is not necessary to provide a positive connection atthe free end. The manual reset function, in accordance with the presentinvention, is obtained in the present instance by the mere addition oftwo parts, namely, the reset member and the retainer. The retainer 33 issecured to the assembled condition by the same rivet 18 which is used tomount the terminal element 19 and the spring arm 21. Therefore the costof manufacturing the parts and the cost of assembly is not increasedmaterially even though the manual reset feature is provided.

Although a preferred embodiment of this invention is illustrated, it isto be understood that various modifications and rearrangements of partsmay be resorted to without departing from the scope of the inventiondisclosed.

What is claimed is:

l. A manual reset thermostat comprising a base, first and secondterminal assemblies mounted on said base, a cantilever spring armmounted on said first terminal assembly and having a free arm portionmovable into and out of engagement with said second terminal assembly,said body providing guide projections on each side of said spring armand a central projection, a bimetallic snap disc having two positions ofstability laterally located by said guide projections and locatedbetween said central projection and said spring arm, said disc when inone position of stability permitting said free arm portion to engagesaid second terminal assembly and when in the other position ofstability maintaining said free arm portion spaced from said secondterminal assembly, and a reset member having a portion extending betweensaid guide projections engagable with said disc on each side of saidspring arm when said disc is in said other position of stability,movement of said reset member to an operative position causing saidportions to cooperate with said central projections and cause movementof said disc toward said one position of stability, and a retainermember mounted in one of said terminal assemblies operating to retainsaid reset member in its assembled position.

2. A manual reset thermostat as set forth in claim 1 wherein saidretainer member is secured to said first terminal and overlies saidspring arm, said retainer member engaging said body on the side of saidsecond terminal remote from said first terminal.

' 3. A manual reset thermostat as set forth in claim 2 wherein saidreset member provides a cross portion position between said spring armand said retainer member.

4. A manual reset thermostat as set forth in claim 3 wherein saidretainer member is formed with an opening substantially coaxial withsaid disc, and said reset member provides a locating projectionextending through said opening.

1. A manual reset thermostat comprising a base, first and secondterminal assemblies mounted on said base, a cantilever spring armmounted on said first terminal assembly and having a free arm portionmovable into and out of engagement with said second terminal assembly,said body providing guide projections on each side of said spring armand a central projection, a bimetallic snap disc having two positions ofstability laterally located by said guide projections and locatedbetween said central projection and said spring arm, said disc when inone position of stability permitting said free arm portion to engagesaid second terminal assembly and when in the other position ofstability maintaining said free arm portion spaced from said secondterminal assembly, and a reset member having a portion extending betweensaid guide projections engagable with said disc on each side of saidspring arm when said disc is in said other position of stability,movement of said reset member to an operative position causing saidportions to cooperate with said central projections and cause movementof said disc toward said one position of stability, and a retainermember mounted in one of said terminal assemblies operating to retainsaid reset member in its assembled position.
 2. A manual resetthermostat as set forth in claim 1 wherein said retainer member issecured to said first terminal and overlies said spring arm, saidretainer member engaging said body on the side of said second terminalremote from said first terminAl.
 3. A manual reset thermostat as setforth in claim 2 wherein said reset member provides a cross portionposition between said spring arm and said retainer member.
 4. A manualreset thermostat as set forth in claim 3 wherein said retainer member isformed with an opening substantially coaxial with said disc, and saidreset member provides a locating projection extending through saidopening.